New (was working fine) QCX+ 20 making loud buzzing, motorbike and clock audio after editing functions.


tony.volpe.1951@...
 

I just got my QRPlabs factory built QCX+20 last week. Worked beautifully for a few days of WSPR and CW. All perfect. Delighted. Big grins.
 
Now all of a sudden, with no known accidents, it has started behaving very oddly.

On switch on, the rig works fine; sensitive receive and faultless transmit. Power normal. 

But then, on entering the edit menus, things started to go wrong. If for example setting time in beacon mode, I can edit the hour digits, but on clicking to enter the minute digits, a loud buzz comes into the headphones. This buzz can turn into a motorbike rapid popping sound as you come out of the menus and it changes volume and frequency as I press the menu editing buttons. Different menu setting modes can result in different amplitude of buzz or tone frequency. The only way to end this annoyance is to power cycle the radio. Then it comes back fine, until you start to edit any parameter and at some point in the editing process, it returns. The onset of the problem is not systematic, it can happen early or late in the edit process, always, I think, as I press the right button to leave a particular menu.

My first line of attack, was to do a factory reset. Forgot I had the TXO and the rig came back with a system frequency of 27MHZ, which for a time lost me my receive, until I figured out the issue and corrected it, but the Buzzing problem was still there.

Reluctantly, I opened the case and examined the board with a jeweller's loupe. I found a couple of dark, 'slaggy' looking, flux deposits on joints and removed them, along with a few small, 1mm sized, solder flakes, which might have made mischief  either now or later. I checked the seating of the AVR, raised it slightly and then re-seated it. The problem was still there on re-assembling the front panel

If I power the set down and reboot. It works normally until I need to change something in the menus.

It can also be brought on by unplugging the key or plugging it. My well used QCX+ 40 does not object to this.

EDIT:

I have removed and re-seated the front panel a couple of times and have found a change in behaviour. There may be an issue in the seating of the panel or the pins, perhaps a dry joint - don't know yet. I have managed to operate the rig menu features a few times without the fault. This persisted until I wiggled the front panel and then it returned. 

I will investigate further. Maybe there is an issue with the front panel and an intermittent connection issue. I don't have time right now to investigate, but in the meantime, If anyone has a clue what might be causing this, I'd appreciate their input. 

Thanks

Tony G0BZB

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